.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later .. c:namespace:: MC .. _request-func-ioctl: *************** request ioctl() *************** Name ==== request-ioctl - Control a request file descriptor Synopsis ======== .. code-block:: c #include ``int ioctl(int fd, int cmd, void *argp)`` Arguments ========= ``fd`` File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`. ``cmd`` The request ioctl command code as defined in the media.h header file, for example :ref:`MEDIA_REQUEST_IOC_QUEUE`. ``argp`` Pointer to a request-specific structure. Description =========== The :ref:`ioctl() ` function manipulates request parameters. The argument ``fd`` must be an open file descriptor. The ioctl ``cmd`` code specifies the request function to be called. It has encoded in it whether the argument is an input, output or read/write parameter, and the size of the argument ``argp`` in bytes. Macros and structures definitions specifying request ioctl commands and their parameters are located in the media.h header file. All request ioctl commands, their respective function and parameters are specified in :ref:`media-user-func`. Return Value ============ On success 0 is returned, on error -1 and the ``errno`` variable is set appropriately. The generic error codes are described at the :ref:`Generic Error Codes ` chapter. Command-specific error codes are listed in the individual command descriptions. When an ioctl that takes an output or read/write parameter fails, the parameter remains unmodified.